P1493: DIAGNOSTIC ACCURACY OF AN AUTOMATED MAGNETIC RESONANCE IMAGE ANALYSIS SYSTEM FOR THE RAPID EVALUATION OF LIVER IRON CONCENTRATION IN PATIENTS WITH HFE RELATED HEMOCHROMATOSIS.
Authors: John B. Porter, Perla Eleftheriou, Emma Drasar, Ryan Mullally, Deepak Suri, Kim Le, James Moon, Stephanie Muth, Tim St Pierre
Journal: HemaSphere (2023)

Topic: 29. Iron metabolism, deficiency and overload Background: MRI is increasingly being used to measure liver iron concentration (LIC) in suspected or diagnosed hemochromatosis. To obtain an LIC result, MR image post-processing is required. An artificial intelligence based software system (DLA R2-MRI) for automatically analyzing MR images to generate LIC values has been developed enabling results to be generated immediately after the scan and eliminating the associated costs of post-processing. DLA R2-MRI requires MR image data acquired in accordance with the spin-density-projection assisted (SDPA) R2-MRI (FerriScan®) method. Aims: The aim of the study was to assess the diagnostic accuracy of the DLA R2-MRI system for evaluation of LIC in patients referred to UCLH with suspected excess liver iron loading related to C282Y and/or H63D variants of the HFE gene using SDPA R2-MRI as the reference method. Methods: Consecutive MR image datasets from all patients referred for assessment of iron overload and submitted for manual SDPA R2-MRI post processing between July 2017 and Oct 2022 were also automatically processed by the DLA R2-MRI system to evaluate LIC. The bias and 95% limits of agreement (LOA) between the LIC results from the index DLA R2-MRI method and the reference SDPA R2-MRI method were calculated using the methods of Bland and Altman. The sensitivity and specificity of the index method relative to the reference method were calculated for the LIC threshold of 2.0 mg Fe/g dw, a threshold above which consideration for therapeutic phlebotomy is recommended [1]. Results: 33 image datasets from 29 patients (22 male) with a mean age of 52.4 (SD 13.2) years were identified that met the inclusion criteria. The patients comprised 16 with C282Y/C282Y, 2 with H63D/H63D, 9 with C282Y/H63D, and 2 with C282Y/wildtype HFE gene variants and were scanned either at diagnosis, or during induction phlebotomy therapy, or in the maintenance phlebotomy phase. One patient contributed 3 and 2 patients contributed 2 image datasets. The index method LIC values are plotted against the reference method LIC values in the figure. The bias of the index method LIC results relative to those of the reference method as a geometric mean ratio was 1.24 (95% CI 1.10 to 1.39). The upper and lower LOA between the index and reference method as ratios of the index LIC results to the reference LIC results were 2.44 and 0.63 respectively. The sensitivity and specificity of the index method for predicting reference method results above 2.0 mg Fe/g dw were 0.83 (95% CI 0.55 to 0.97) and 0.90 (95% CI 0.71 to 0.98) respectively. Summary/Conclusion: A positive bias of the index method relative to the reference method was observed in contrast to the smaller negative bias observed on a larger study of 1281 image datasets from patients with varied etiologies for liver iron loading [2]. The span of the LOA between the index and reference method in this study was similar to those observed in the larger study involving heterogeneous causes of iron overload. The sensitivity and specificity of the index method for predicting reference method results above 2.0 mg Fe/g dw were moderate but with very wide confidence intervals owing to the small number of cases in the study. Overall the agreement between the index and the reference methods is sufficient over the LIC range examined to determine whether iron overload exists, as well as its extent, in patients with one or more HFE variant genes. Furthermore, results are delivered rapidly so that they can be given to the patient on the same day as scanning. 1.Girelli, et al. (2022) Blood, 139: 3018. 2.St Pierre, et al. (2022) HemaSphere, 6: 2639.Keywords: Artificial intelligence, MRI, Liver iron concentration